Imaging systems that utilize high energy radiation (such as x-rays) to sample an object to be imaged are known in the art. Many such systems employ one or more high-energy sources that form corresponding fan beams of high energy. One or more detectors then detect the extent to which the object interacts with this high energy (for example, by absorbing some portion of that energy). By providing relative motion of the source/detector with respect to the object a series of such images can be assembled to form a composite image of the object.
Unique problems arise when attempting to employ such approaches when the source/detector and the object move relatively quickly with respect to one another. For example, such an approach is theoretically applicable for use in sampling a fast-moving object such as a railroad train. A practical realization of this approach, however, encounters numerous significant obstacles. As one example in this regard, the pulse periodicity of a single energy source may be too slow to permit a train to be completely sampled as the train speeds past the imaging system. Consider that a typical sampling requirement might be a 5 mm sample pitch. With a 1 ms sample period (admittedly high but nevertheless achievable) and a 15 m/s velocity, however, the spacing between samples for one sampling chain 100 is 15 mm. If the detector width demagnified into the object plane is 5 mm, this single sampling chain 101 would then have 5 mm wide vertical bands with 10 mm blank spaces separating them. The resultant composite image would therefore be missing ⅔rds of the train.
Using a plurality of sources/detectors in such a case to capture the remainder of the object, in turn, also encounters numerous speed-related problems. In particular, one can quickly conclude that an inappropriately large number of such sampling chains are potentially required in order to attempt capturing a complete set of samples for a fast-moving object and even this may prove insufficient; there may still be unacceptable gaps in the information so captured. This can lead to a variety of intractable problems including a physical inability to accommodate all of the sampling chains, a practical inability to make the financial investment necessary to acquire or operate the sampling chains, and so forth.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.